The present invention relates to an apparatus, in particular to an apparatus for removing “rejects” that is of use in a method for extracting bitumen from an oil sand stream. Further, the present invention relates to a method for extracting bitumen from an oil sand stream whilst using the apparatus.
Various methods have been proposed in the past for the recovery of bitumen (sometimes referred to as “tar” or “bituminous material”) from oil sands as found in various locations throughout the world and in particular in Canada such as in the Athabasca district in Alberta and in the United States such as in the Utah oil sands. Typically, oil sand (also known as “bituminous sand” or “tar sand”) comprises a mixture of bitumen (in this context also known as “crude bitumen”, a semi-solid form of crude oil; also known as “extremely heavy crude oil”), sand, clay minerals and water. Usually, oil sand contains about 5 to 25 wt. % bitumen (as meant according to the present invention), about 1 to 13 wt. % water, the remainder being sand and clay particles.
As an example, it has been proposed and practiced at commercial scale to recover the bitumen content from the oil sand by mixing the oil sand with water and separating the sand from the aqueous phase of the slurry formed.
Other methods have proposed non-aqueous extraction processes to reduce the need for large quantities of process water.
A problem of known methods of extraction of bitumen from oil sand is the handling of the rejects, i.e. the relatively large lumps such as stone and clay that remain intact after the oil sand stream has been contacted with solvent.
It is an object of the present invention to improve the handling of such rejects.
It is a further object of the present invention to provide a more efficient handling of rejects in an oil sand stream, in particular when bitumen is to be extracted from the oil sand stream using a non-aqueous solvent, which non-aqueous solvent needs to be removed from the rejects prior to disposal.